Bradykinin

• Bradykinin is a nonapeptide that functions as a potent vasodilator and mediator of inflammation. It is part of the kallikrein-kinin system.
• Bradykinin Plays a key role in inflammation and blood pressure regulation.

Synthesis:

• Prekallikrein Activation: Kallikrein converts high-molecular-weight kininogen to bradykinins.
• Regulation: Degraded by angiotensin-converting enzyme (ACE), which is why ACE inhibitors increase bradykinins levels.

Functions of Bradykinin:

• Vasodilation: Causes blood vessels to dilate, lowering blood pressure.
• Increased Vascular Permeability: Leads to edema and inflammation.
• Pain Induction: Stimulates sensory nerves to produce pain.
• Smooth Muscle Contraction: Influences bronchoconstriction and gastrointestinal motility.

Receptors:

1. B1 Receptors: Induced during inflammation; involved in chronic inflammatory responses.
2. B2 Receptors: Constitutively expressed; mediate most of the acute effects of bradykinins.

Clinical Relevance of Bradykinin:

• ACE Inhibitors Side Effects: Increased bradykinins levels are associated with the cough and angioedema seen in some patients.
• Potential Therapeutic Targets: Modulating bradykinins pathways for treating inflammatory diseases and pain.

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